KR102818330B1 - Strip-shaped composite material for probe needles - Google Patents

Abstract

The present invention relates to a strip-shaped sandwich composite material for producing a probe needle, wherein an inner core layer (1) is arranged between two outer cover layers (2, 3), the inner core layer (1) being composed of a palladium alloy comprising at least 30 wt. % palladium or a platinum alloy comprising at least 30 wt. % platinum, and the two outer cover layers (2, 3) being composed of a precipitation-hardening and/or dispersion-hardening copper alloy comprising at least 90 wt. % copper and/or a precipitation-hardening and/or dispersion-hardening silver alloy comprising at least 70 wt. % silver.
The present invention also relates to methods for producing probe needles, bonding strips, probe needle arrays, and composite materials.

Description

{STRIP-SHAPED COMPOSITE MATERIAL FOR PROBE NEEDLES}

The present invention relates to a strip-shaped, sandwich-shaped layered composite material from which probe needles for electronic testing of semiconductor devices can be punched or cut, and to probe needles, bonding strips and probe needle arrays produced from or using the strip-shaped sandwich-shaped layered composite material.

The present invention also relates to a method for producing such strip-shaped, sandwich-type layered composite materials of two different materials from strips.

In addition to the probe needle, a bonding strip or bonding wire having the same physical properties as the probe needle can also be manufactured from the composite material. The bonding strip is a strip-shaped bonding wire.

During chip manufacturing, after processing, the wafer is directly contacted by probe needles in an unsawn state to test the functionality of the integrated circuit (IC). In this case, after the structuring of the individual chips, an array of probe needles tests the functionality of the semiconductor wafer. The probe needles are fixed to a test card (probe card) that matches the wafer design. During the test process, the wafer is pressed against the probe needles, and contact is made between the probe needles and the pads of the IC. Various parameters such as contact, electrical characteristics at high current densities, and electrical behavior during temperature changes are then tested.

Probe needles are therefore used in the manufacture of power electronics, contacting chips and other electrical circuits for testing the quality of electrical contacts (see, for example, US 2014/0266278 A1 and US 2010/0194415 A1).

In applications such as probe needles or bonding strips in power electronics, high mechanical strength and hardness are required in addition to high electrical conductivity. In addition, temperature resistance or heat resistance is very important.

Key parameters of an excellent probe needle include high hardness to keep maintenance intervals low as well as high electrical conductivity, since high currents have to be transmitted during testing of power electronics ICs. Furthermore, the probe needles and bonding strips utilize a low elastic modulus (m _E ) and a high yield strength (Rp _0.2 ), which produce excellent spring properties. A high thermal conductivity results in an excellent dissipation of thermal energy and thus keeps the additional thermal increase in electrical resistance as low as possible. Suitable hardness, elastic modulus and yield strength are required to firstly keep maintenance intervals low and secondly to realize the excellent spring properties of the probe needle.

The electrical conductivity of pure copper (100% IACS = 58.1 * 10 ⁶ S/m) serves as a standard for determining electrical conductivity. However, pure copper (Cu) and pure silver (Ag) cannot be used for this purpose because they are too ductile and the probe needle deforms during use.

In applications such as probe needles or bonding strips in power electronics, high mechanical strength and hardness are required in addition to high electrical conductivity. In this case, temperature resistance or heat resistance is also very important.

As materials for probe needles, precipitation-hardening copper alloys, rhodium alloys (Rh alloys) or palladium alloys (Pd alloys) are currently used, which are processed by cold casting, solution annealing, precipitation heat treatment and rolling to form thin strips with a thickness of less than 55 μm.

For use in gold pads, palladium alloys such as Paliney® H3C from Deringer Ney or NewTec® from Advanced Probing are known. Typical materials for probe needles may contain 10 wt.% gold and 10 wt.% platinum, for example, precipitation-hardening palladium-silver alloys sold under the names Paliney® 7, Hera 6321, and Hera 648. US 2014/377 129 A1 and US 5 833 774 A disclose hardening Ag-Pd-Cu alloys for electrical applications. These alloys have a high hardness of 400 to 500 HV. However, their electrical conductivity is rather low, at 9 to 12% IACS. High electrical conductivity is an important factor for probe needles.

For testing on aluminum pads, probe needles made of tungsten, tungsten carbide, palladium-copper-silver alloy and tungsten rhenium materials are widely used. The latter are particularly hard, and aluminum pads are more rigid than gold pads, so that tests with hard needles can be better tolerated than with gold pads. These probe needles also do not have very high electrical conductivity. Higher electrical conductivity alloys, such as CuAg7, are less hard (about 320 HV1) and less heat resistant than palladium-silver or palladium-copper-silver alloys.

Additionally, PtNi30 alloys for probe needles are available on the market. US 2010/0239453 A1 and EP 2-248 920 A1 disclose low-doped iridium alloys for the production of probe needles.

US 2006/0197542 A1 discloses a platinum series alloy for producing a probe needle. The alloy has a high hardness of 300 HV to 500 HV so as to produce excellent contact by a lacquer layer arranged on a gold pad.

In principle, suitable palladium-copper-silver alloys are already known from US 1 913 423 A and GB 354 216 A. Palladium-copper-silver alloys can form structures with superlattices, which can improve the electrical conductivity and the mechanical stability of the alloy. The atoms in the lattice are then no longer randomly distributed, but are arranged in a periodic structure, the superlattice. As a result, hardnesses of more than 350 HV1 (Vickers hardness test according to DIN EN ISO 6507-1:2018 to -4:2018 with a test force of 9.81 N (1 kilopond)), electrical conductivities of more than 19.5 % IACS, and rupture strengths of up to 1500 MPa are possible. Palladium alloys, such as the palladium-copper-silver-ruthenium/rhodium alloy known from EP 3 960 890 A1 and platinum series alloys known from the prior art have very good mechanical properties even at high temperatures, but their electrical and thermal conductivities are less good compared to copper and copper alloys.

However, PtNi alloy (platinum-nickel alloy) or rhodium (Rh) are also used as film materials for the production of probe needles. For these metals or alloys, which exhibit the best possible compromise between electrical conductivity, thermal conductivity, tensile strength and hardness, the maximum possible electrical conductivity is between 5% and 30% IACS, which is therefore somewhat lower compared to copper.

US 10 385 424 B2 discloses a palladium-copper-silver alloy additionally containing up to 5 wt.% rhenium. This palladium-copper-silver alloy is commercially available under the product name Paliney® 25. In this way, the electrical conductivity can be significantly increased and values of more than 19.5% IACS can be reached. However, the disadvantage here is that rhenium has a very high melting point of 3180° C and therefore has to be alloyed with other metals in a complex manner.

WO 2016/009293 A1 proposes a probe needle, wherein the tip is arranged in front of the probe needle, the tip consists of a mechanically hard first material and the remainder of the probe needle consists of a second material having high electrical conductivity. Similar probe needles are also known from US 2013/0099813 A1, US 2016/0252547 A1, EP 2 060 921 A1 and US 2012/0286816 A1. US 2019/0101569 A1 proposes a sheathed wire comprising such a tip, wherein the tip is only fastened to the wire core of the sheathed wire. In this case, the sheathed wire has to have a wire core with a single coating. The disadvantage here is that the probe needle no longer has homogeneous physical properties over its length, and not only the electrical and thermal conductivity but also the tensile strength very significantly depends on the bond between the two materials. Moreover, low electrical conductivity in one region cannot simply be compensated for by high electrical conductivity in another region, as is the case in a series circuit of electrical resistors, since the current must pass through both regions.

As composite wires for producing probe needles or bonding wires, it is possible, for example, to use wires which are coated all around, which can be produced by a continuous rolling process or by galvanic coating as what are known as coated wires or double wires. For example, in the field of contact technology, for example as sliding contacts in slip ring transmitters or also as switching contacts in microswitches, as described in DE 10 2019 130 522 A1, these can have, on the inside, a non-precious metal, for example a Cu alloy such as CuBe2 coated with a precious metal alloy (e.g. Hera238).

To improve the electrical conductivity of the probe needle, pure copper is now also galvanically deposited on the palladium alloy. A galvanic coating of a rhodium-based alloy for producing a clad wire as a probe needle is known from EP 3 862 759 B1. Additional coated probe needles are known from WO 2016/107729 A1, US 2017/0307657 A1 and US 2014/0176172 A1.

The disadvantage here is that pure copper has only low hardness and heat resistance, and poor spring properties, and as a result the mechanical properties of composite materials produced in this way from palladium alloys and copper are negatively affected.

It would therefore be desirable to improve the galvanically coated palladium alloy so that an improvement in electrical conductivity can be achieved without, or with less, simultaneous degradation of the mechanical properties of the composite material and the probe needle or bonding strip produced therefrom.

It is therefore an object of the present invention to overcome the disadvantages of the prior art. In particular, it is to be found a composite material for producing (specifically by punching or cutting) probe needles for electronic testing of semiconductor devices, and a method for producing such a composite material, wherein the mechanical properties, in particular the tensile strength and the high-temperature tensile strength and preferably also the hardness, as well as the electrical conductivity are improved compared to a palladium alloy, without deterioration in this process in the same way as when using a palladium alloy galvanically coated with pure copper. The composite material and the method should be simple and inexpensive to realize and suitable for mass production. The probe needle and the bonding strip should be able to be produced from the composite material in as simple and cost-effective a manner as possible, the tip of the probe needle preferably being intended to consist of a hard palladium alloy or a platinum alloy. Furthermore, the composite material should have a bond between the materials of the composite material that is as mechanically stable as possible.

The object of the present invention is achieved by a composite material according to claim 1, by a probe needle or a bonding strip according to claim 9, by a probe needle array according to claim 11, by the use of a composite material, a probe needle or a probe needle array according to claim 12 and by a method according to claim 13. Preferred embodiments are disclosed in dependent claims 2 to 8, 10, 14 and 15.

The object of the present invention is achieved by a composite material for producing a probe needle for electronic testing of semiconductor devices, the composite material being strip-shaped and defined by two mutually parallel major surfaces, the composite material having a sandwich structure which is laminated perpendicularly to the parallel major surfaces and which comprises an inner core layer and two outer cover layers, the inner core layer being arranged between the two outer cover layers, the inner core layer being rigidly connected to the two outer cover layers on two opposite sides, the two outer cover layers forming parallel major surfaces, the inner core layer being composed of a palladium alloy comprising at least 30 wt. % palladium or a platinum alloy comprising at least 30 wt. % platinum, and the two outer cover layers being composed of a precipitation-hardening and/or dispersion-hardening copper alloy comprising at least 90 wt. % copper, or a precipitation-hardening and/or dispersion-hardening silver alloy comprising at least 70 wt. % silver, or at least 90 wt. A precipitation-hardening and/or dispersion-hardening copper alloy comprising at least 70 wt.% copper and a precipitation-hardening and/or dispersion-hardening silver alloy comprising at least 70 wt.% silver.

Precipitation-hardening copper and silver alloys produce high hardness and tensile strength.

Dispersion-hardening copper and silver alloys produce high hardness and tensile strength even at high temperatures.

The precipitation-hardening and/or dispersion-hardening copper alloy and the precipitation-hardening and/or dispersion-hardening silver alloy may be both precipitation-hardening and dispersion-hardening.

In the case of precipitation hardening of the alloy, the precipitation of the alloy results from the temperature treatment. In the case of dispersion hardening of the alloy, the dispersoids are distributed within the alloy. The dispersoids may be distributed as particles within the melt prior to solidification. These dispersoids are often oxides or borides, and according to the present invention are preferably metal oxides.

The parallel major surfaces form the largest surface of the strip-shaped composite material. The parallel major surfaces preferably form at least 50% of the surface of the strip-shaped composite material, particularly preferably the parallel major surfaces form at least 90% of the surface of the strip-shaped composite material, and very particularly preferably the parallel major surfaces form at least 99% of the surface of the strip-shaped composite material.

The strip-shaped composite material is preferably in the shape of a flat cube, to a first approximation or a better approximation.

The two outer cover layers can be composed of different copper alloys or silver alloys. It is also possible that one of the two outer cover layers is composed of a copper alloy and the other of the two outer cover layers is composed of a silver alloy. However, it is preferred according to the invention that the two outer cover layers are composed of the same copper alloy or silver alloy, particularly preferably of the same copper alloy.

The principal surfaces which are parallel to each other do not have to form perfectly parallel or plane-parallel surfaces in the mathematical sense. It is sufficient if the principal surfaces which are parallel to each other are inclined to each other at an angle of at most 5°. Preferably, the principal surfaces which are parallel to each other are inclined to each other at an angle of at most 1°.

The principal surfaces which are parallel to each other are also preferably plane-parallel.

Preferably, the major surfaces which are parallel to each other are flat surfaces. Here, a flat surface does not mean a surface which is atomic-wide flat, but rather a flat surface as produced during rolling.

Probe needles and bonding strips can be produced from strip-shaped composite materials by cutting strips of the composite material perpendicularly to the parallel major surfaces or also diagonally to the parallel major surfaces. Additionally, one end of the needle can be pointed, preferably in such a way that the material of the inner core layer forms a tip of the probe needle. This tip can then be used to test the semiconductor structure for its electrical conductivity by pressing the tip onto a semiconductor surface to be examined and measuring the electrical conductivity through the probe needle.

In this case, impurities are understood to mean impurities resulting from the synthesis of all relevant elements.

If the material can be used as a probe needle, it is also suitable for use as a bonding strip or bonding wire.

The inner core layer and the two outer cover layers are preferably metallic.

Precipitation-hardening and dispersion-hardening copper and silver alloys produce high hardness and tensile strength of composite materials even at high temperatures (approximately 300°C).

Preferably, it may be provided that the inner core layer is joined to the two outer cover layers, in particular by roll bonding.

The thickness of the strip-shaped composite material may be specified to be at most 300 μm, and preferably at most 100 μm.

The thickness of the composite material corresponds to the distance between the two major planes formed by the outer surfaces of the two outer cover layers.

Thicker composite materials cannot be readily used as probe needles by cutting or punching the composite material without additional rolling.

Additionally, the thickness of the inner core layer may be defined to be at least equal to the thickness of the two outer cover layers, preferably at least twice as thick as the thickness of the two outer cover layers.

Additionally, the thickness of the inner core layer may be defined to be at most 10 times thicker than the thickness of the two outer cover layers, preferably at most 5 times thicker than the thickness of the two outer cover layers, particularly preferably at most 3 times thicker than the thickness of the two outer cover layers.

This ensures that the physical properties of the composite are determined by both the materials of the cover layers and the core layer.

The inner core layer may be defined as being directly connected to the two outer cover layers.

This means that additional layers, such as an adhesive layer and/or a diffusion protection layer, are not arranged between the inner core layer and the two outer cover layers.

These measures make the production of composite materials easy and cost-effective. It has been found that when producing the composite material according to the invention with the method according to the invention, no additional intermediate layers are necessary. During the roll bonding and the subsequent heat treatment, a diffusion layer can be produced between the inner core layer and the two outer cover layers. This is not to be regarded as a separate (additional) layer in the sense of the invention, but as a connection in the region of the boundary surface between the inner core layer and the two outer cover layers.

Additionally, the composite material may be defined as consisting of an inner core layer and outer cover layers.

This makes it clear that the composite material does not require any additional layers or parts. As a result, the composite material is cost-effective to produce.

Alternatively, for example, the two outer cover layers may be coated on the main surfaces or the material may be applied to the edge of the composite material for electrical contact with the probe needle.

It may also be provided that the two outer cover layers consist of a precipitation-hardening and/or dispersion-hardening copper alloy comprising at least 90 wt.% copper, preferably a precipitation-hardening and/or dispersion-hardening copper alloy comprising at least 97 wt.% copper, particularly preferably a precipitation-hardening and/or dispersion-hardening copper alloy comprising at least 99 wt.% copper.

Precipitation-hardening and dispersion-hardening copper alloys with high copper content are particularly well suited for the production of probe needles because they have high electrical conductivity while also having relatively high hardness and tensile strength for high copper content copper alloys.

Preferably, it may also be provided that the inner core layer consists of a palladium alloy containing at least 30 wt.% palladium, preferably a palladium alloy containing at least 35 wt.% palladium, particularly preferably a palladium-copper-silver alloy according to EP 3 960 890 A1.

Preferably, the inner core layer is composed of a palladium-copper-silver alloy containing at least 35 wt.% palladium, at least 20 wt.% copper and at least 20 wt.% silver, particularly preferably a palladium-copper-silver alloy containing at most 31 wt.% copper and 29 wt.% silver, the remainder of palladium comprising impurities.

Particularly preferably, the inner core layer consists of a palladium-copper-silver alloy according to EP 3 960 890 A1. In this case, particularly preferred palladium-copper-silver alloys are described in paragraph [0013] of EP 3 960 890 A1. Very particularly preferred embodiments are described in paragraphs [0021] to [0048] and [0067] of EP 3 960 890 A1.

These palladium alloys produce particularly high tensile strength and heat resistance of composite materials, which are then used to produce such probe needles and bonding strips.

Additionally, the composite material can be defined as having an electrical conductivity of at least 35% IACS (20.3 10 ⁶ S/m), preferably at least 40% IACS (23.2 10 6 S/m), particularly preferably at least 45% IACS (26.1 10 ⁶ S/m), measured at room temperature using a four-point measurement method on one of the two outer cover layers.

Additionally, it can be specified that the composite material has a Vickers hardness HV0.05 of at least 170, preferably at least 190, particularly preferably at least 196 at room temperature in the two covering layers.

Additionally, the composite material may be specified to have a tensile strength of at least 1000 MPa, preferably at least 1100 MPa, parallel to the plane of the inner core layer at room temperature.

Additionally, the composite material may be specified to have a yield strength of at least 950 MPa, preferably at least 1050 MPa, parallel to the plane of the inner core layer at room temperature.

These physical properties of the composite material can be realized by the composite material according to the present invention, and can bring about advantageous material properties for the probe needle and bonding strip produced therefrom. In particular, the combination of these physical properties results in very excellent properties for the probe needle and bonding strip. In particular, the combination of high electrical conductivity and high tensile strength is advantageous for the probe needle and bonding strip.

The electrical conductivity can be determined by four-pole measurements of the voltage drop on a test object over a defined length, using a Burster Resistomat 2316. The measurements are performed on the major surfaces of the composite material having an edge length of 5 mm or more, a thickness of 55 μm and a measuring current of 10 mA.

Additionally, it may be specified that the composite material has a 0.2% yield point (Rp _0.2 ) (elastic limit) at room temperature of at least 1000 MPa, preferably at least 1150 MPa, particularly preferably at least 1300 MPa.

These mechanical and electrical properties, and particularly their combination, ensure that the composite material has particularly good elastic properties and high electrical conductivity, enabling it to be used as probe needles or bonding strips.

The 0.2% yield point (Rp _0.2 ) can be determined using a Zwick tensile tester Z250. The tensile test can be performed on composite materials with a thickness of 50 μm and a width of 13 mm, and is based on the present specification. The test speed for the yield strength Rp _0.2 is 1 mm/min.

Furthermore, the precipitation-hardening and/or dispersion-hardening copper alloy may be defined as a precipitation-hardening and/or dispersion-hardening copper-chromium alloy comprising at least 98 wt.% copper, in particular a precipitation-hardening and/or dispersion-hardening CuCr1Zr alloy comprising at least 0.5 wt.% and at most 1.2 wt.% chromium, at least 0.03 wt.% and at most 0.3 wt.% zirconium, the remainder copper comprising impurities.

Additionally, the precipitation-hardening and/or dispersion-hardening copper alloy may be defined as a precipitation-hardening copper-chromium-titanium alloy comprising at least 99 wt.% copper, in particular a precipitation-hardening copper-chromium-titanium-silicon alloy comprising 0.3 wt.% chromium, 0.1 wt.% titanium, 0.02 wt.% Si and the remainder copper comprising impurities.

Additionally, the precipitation-hardening and/or dispersion-hardening copper alloy may be defined as a precipitation-hardening copper-chromium-silver alloy comprising at least 98 wt.% copper, in particular a precipitation-hardening copper-chromium-silver-iron-titanium-silicon alloy comprising 0.5 wt.% chromium, 0.2 wt.% silver, 0.08 wt.% iron, 0.06 wt.% titanium, 0.03 wt.% Si and the remainder copper comprising impurities.

Such copper alloys are particularly preferred according to the present invention.

Furthermore, the precipitation-hardening and/or dispersion-hardening copper alloy may be defined as a precipitation-hardening and/or dispersion-hardening copper-silver alloy comprising at least 90 wt.% copper, in particular at least 3 wt.% silver and at most 7 wt.% silver, and the remainder copper comprising impurities, or a precipitation-hardening and/or dispersion-hardening copper-silver alloy comprising impurities, the remainder copper comprising oxidizing dispersants and at most 0 wt.%.

Such copper alloys containing 3 wt.% silver (CuAg3) are particularly preferred according to the present invention.

Additionally, the precipitation-hardening and/or dispersion-hardening silver alloy may be defined as a silver-copper alloy comprising at least 70 wt.% silver, preferably a silver-copper alloy comprising at least 9 wt.% copper and at most 29 wt.% copper and the remainder silver comprising impurities, particularly preferably a silver-copper alloy comprising 10 wt.% copper and the remainder silver comprising impurities, or a silver-copper alloy comprising 28 wt.% copper and the remainder silver comprising impurities.

Furthermore, the palladium alloy is a palladium-copper-silver alloy comprising palladium as a main component, the palladium-copper-silver alloy having a weight ratio of palladium to copper of at least 1.05 and at most 1.6 and a weight ratio of palladium to silver of at least 3 and at most 6, the palladium-copper-silver alloy may be defined as containing more than 1 wt. % and at most 6 wt. % ruthenium, rhodium or ruthenium and rhodium, and at most 1 wt. % of other metal elements comprising palladium, copper and silver and impurities, preferably less than 0.3 wt. % iridium, as the remainder.

Such palladium-copper-silver alloys are particularly preferred according to the present invention.

A weight ratio of palladium to copper of at least 1.05 and at most 1.6 means that palladium is contained in the palladium-copper-silver alloy in an amount of at least 105% and at most 160% by weight of the copper contained in the palladium-copper-silver alloy.

Therefore, a weight ratio of palladium to silver of at least 3 and at most 6 means that palladium is contained in the palladium-copper-silver alloy in an amount at least 3 times and at most 6 times the weight of silver contained in the palladium-copper-silver alloy.

Additionally, the palladium alloy may be defined as a palladium-silver-copper-platinum alloy, particularly a palladium-silver-copper-platinum-zinc-gold alloy comprising 38 wt. % silver, 15 wt. % copper, 1.5 wt. % platinum, 1 wt. % zinc, 0.5 wt. % gold, and the remainder palladium comprising impurities, or a palladium-copper-platinum-gold-zinc alloy comprising 30 wt. % silver, 14 wt. % copper, 10 wt. % platinum, 10 wt. % gold, 1 wt. % zinc, and the remainder palladium comprising impurities.

Additionally, the palladium alloy may be defined as a palladium-copper-silver-ruthenium alloy, particularly a palladium-copper-silver-ruthenium alloy comprising 36.5 wt. % copper, 10.5 wt. % silver, 1.5 wt. % ruthenium, and the remainder palladium comprising impurities, or a palladium-copper-silver-ruthenium-rhenium alloy comprising 36.5 wt. % copper, 10.5 wt. % silver, 1.1 wt. % ruthenium, 0.4 wt. % rhenium, and the remainder palladium comprising impurities.

Additionally, the palladium alloy may be defined as a palladium-copper-silver-rhodium alloy, particularly a palladium-copper-silver-rhodium alloy comprising 36.5 wt.% copper, 10.5 wt.% silver, 1.5 wt.% rhodium, and the remainder palladium including impurities.

Additionally, the palladium alloy may be defined as a palladium-copper-silver alloy, particularly a palladium-copper-silver alloy comprising 31 wt.% copper, 29 wt.% silver, and the remainder palladium comprising impurities.

Additionally, the palladium alloy may be defined as a palladium-silver-copper alloy, particularly a palladium-silver-copper alloy comprising 38 wt.% silver, 15 wt.% copper, and the remainder palladium including impurities.

Additionally, the platinum alloy may be defined as a platinum-nickel alloy, preferably a platinum-nickel alloy comprising at least 3 wt.% and at most 10 wt.% nickel, and the remainder platinum comprising impurities, particularly preferably a platinum-nickel alloy comprising 5 wt.% nickel, and the remainder platinum comprising impurities.

In the above-mentioned alloys, the element having the highest proportion by weight in the alloy is always mentioned first. Preferably, the element having the second highest proportion by weight in the alloy is preferably mentioned second. Particularly preferably, the element having the third highest proportion by weight in the alloy is mentioned third. Very particularly preferably, in the case of the mentioned alloys, the mentioned alloying components are arranged in order according to their proportion by weight.

In this case, the principal component is understood to mean the element (in this case palladium, platinum, copper or silver) which is the main, i.e., most abundant component in terms of quantity, i.e., for example, a palladium-copper-silver alloy contains more palladium than copper or silver.

Such alloys are particularly well suited for producing composite materials according to the present invention.

The precipitation-hardening and/or dispersion-hardening copper alloy may comprise at most 2 wt. % precipitates and/or dispersions, preferably at most 1 wt. % precipitates and/or dispersions, wherein the precipitates and/or dispersions may be defined as consisting of at least 95 wt. % of at least one element selected from the list consisting of chromium, titanium, silicon, iron, oxygen, zirconium and silver.

These small amounts of precipitates and/or dispersoids are sufficient to improve the hardness of the copper alloy and, where applicable, also the silver alloy, without significantly reducing the electrical conductivity.

The proportion of precipitates and/or dispersions can be determined by evaluating a cross-section of the copper alloy with a scanning electron microscope or also with a light microscope, in relation to the surface ratio of precipitates and/or dispersions to the total area of the copper alloy, it being necessary for the density of the precipitates and/or dispersions and the matrix surrounding them to be taken into account for the present study. The density can be determined, for example, on the basis of a composition analysis by energy-dispersive or wavelength-dispersive X-ray analysis (EDX or WDX) or by X-ray fluorescence.

The precipitation-hardening and/or dispersion-hardening silver alloy may be defined as comprising at most 2 wt.% precipitates and/or dispersions, preferably at most 1 wt.% precipitates and/or dispersions, wherein the precipitates and/or dispersions consist of at least 95 wt.% of at least one element selected from the list consisting of chromium, titanium, silicon, iron, oxygen, zirconium and copper.

Additionally, the inner core layer may be defined as being composed of a precipitation-hardening and/or dispersion-hardening palladium alloy, or a precipitation-hardening and/or dispersion-hardening platinum alloy.

This improves the tensile strength of the composite material and the stability of the needle tip of the probe needle produced therefrom. Preferably, the inner core layer is composed of a precipitation-hardening and/or dispersion-hardening palladium alloy.

The object upon which the present invention is based is also achieved by a probe needle or bonding strip comprising a strip of the composite material described above.

Probe needles and bonding strips benefit from the favorable physical properties of the composite material.

In this case, the probe needle may be defined as having a tip made of the material of the inner core layer.

This achieves high stability of the probe needle. Probe needles with this tip can consequently be used very frequently without having to be replaced or adjusted very frequently.

The object upon which the present invention is based is further achieved by a probe needle array comprising a plurality of the aforementioned probe needles arranged in parallel with one another.

The objects upon which the present invention is based are also achieved by the use of the above-described composite material or the above-described probe needle or the above-described probe needle array for testing electrical contact or for creating electrical contact or sliding contact.

The objects on which the present invention is based are further achieved in a method for producing a composite material of two metal alloys, the composite material being suitable for producing probe needles for electronic testing of semiconductor devices, and for this purpose, a method is provided, characterized by the following chronologically sequential steps:

A) providing a first strip of a palladium alloy comprising at least 30 wt. % palladium or a platinum alloy comprising at least 30 wt. % platinum, and a second strip of a precipitation-hardening and/or dispersion-hardening copper alloy comprising at least 90 wt. % copper or a precipitation-hardening and/or dispersion-hardening silver alloy comprising at least 70 wt. % silver, and a third strip of a precipitation-hardening and/or dispersion-hardening copper alloy comprising at least 90 wt. % copper, or a precipitation-hardening and/or dispersion-hardening silver alloy comprising at least 70 wt. % silver,

B) a step of arranging the first strip between the second strip and the third strip, and positioning the first strip against the second strip and the third strip, and

C) a step of connecting the first strip to the second strip and the third strip by roll joining the strips positioned opposite each other, the roll joining producing a continuous strip-shaped composite material from the materials of the first strip, the second strip and the third strip.

Preferably, during the roll joining, the thicknesses of the first strip, the second strip and the third strip are reduced.

Roll bonding can be performed in a number of steps, with each step reducing the thickness of the composite material.

In the method according to the present invention, it may be provided that step D) is performed after step C):

D) Temperature treatment of the composite produced in step C), the material of the first strip is precipitation-hardened and/or dispersion-hardened during the temperature treatment.

As a result of the downstream temperature treatment, the strips can be well connected to each other in advance by the rolling mill.

Additionally, it may be provided that the composite material described above is produced by the method, or that at least one probe needle described above or at least one bonding strip described above is produced by the method by cutting or punching the composite material, or preferably that a plurality of probe needles or bonding strips described above are produced by the method by cutting or punching.

The present invention is based on the surprising discovery that solid and hard palladium alloy or platinum alloy layers can be coated on both sides with a precipitation-hardening copper alloy and/or silver alloy having a higher electrical conductivity in order to produce sandwich-shaped and strip-shaped composite materials, the mechanical properties of which are improved in relation to tensile strength and heat resistance and hardness compared to palladium alloys or platinum alloys coated with pure copper or pure silver, while at the same time a significant increase in the electrical conductivity is achieved compared to pure hard palladium alloys or platinum alloys. Surprisingly, it has been found in the context of the present invention that such coatings with precipitation-hardening copper alloys and/or silver alloys can be realized with the aid of a roll-bonding process, which would not be possible to produce by galvanic coating. The invention is furthermore based on the discovery that when they have similar hardness, the core layer and the two outer cover layers can be well joined to one another by roll bonding.

The preferred composite material according to the invention consisting of a copper and palladium alloy for line materials or probe needles advantageously combines the positive properties of a copper alloy (high electrical conductivity) and a palladium alloy (high heat resistance and excellent spring properties). This provides a material having a better conductivity than conventional palladium alloys (Hera 6321® or Paliney H3C®) and a better heat resistance and overall hardness than CuAg7. The copper alloy used has about 80% of the electrical conductivity of pure copper and four times the strength of pure copper and therefore has considerably better overall properties. These alloys used during roll joining cannot be deposited using galvanic processes, which are generally limited to pure metals and a few selected alloys.

To achieve advantageous property combinations, multiple different layers of different metals and noble metals can also be applied galvanically. However, precipitation-hardening alloys are not deposited in this way, which makes the process very complicated. During the final heat treatment, there is also the risk of diffusion, which negatively affects the electrical conductivity due to the formation of mixed crystals.

Work-hardening of a palladium alloy galvanically coated with copper by further rolling can also be considered. However, consistent properties cannot be expected, since the copper and palladium alloys have significantly different hardnesses, which leads to non-uniform deformation.

Additional embodiments of the present invention are described below with reference to four schematic drawings, but are not intended to limit the present invention. In the drawings:
Figure 1 illustrates a schematic cross-sectional view through details of a composite material according to the present invention.
FIG. 2 is a schematic cross-sectional perspective view illustrating details of a composite material according to the present invention according to FIG. 1.
FIG. 3 shows a photomicrograph of a polished cross-section of a composite material according to the present invention.
FIG. 4 illustrates a photomicrograph of a polished cross-section of an additional composite material according to the present invention.
Figure 5 illustrates a flow chart of a method according to the present invention.
Figures 1 and 2 illustrate schematic cross-sections through a composite material according to the present invention. The cross-sections are shown hatched.

The composite material has an inner core layer (1) and two outer cover layers (2, 3).

The inner core layer (1) is composed of a palladium alloy containing at least 30 wt.% palladium or a platinum alloy containing at least 30 wt.% platinum. Each of the two outer cover layers (2, 3) can be composed of a precipitation-hardening and/or dispersion-hardening copper alloy containing at least 90 wt.% copper, or a precipitation-hardening and/or dispersion-hardening silver alloy containing at least 70 wt.% silver.

Preferably, the inner core layer (1) consists of a palladium alloy as described in EP 3 960 890 A1.

The two outer cover layers (2, 3) preferably consist of a precipitation-hardening and/or dispersion-hardening copper alloy comprising at least 90 wt.% copper, particularly preferably a precipitation-hardening copper alloy comprising at least 98 wt.% copper.

The inner core layer (1) and the two outer cover layers (2, 3) are firmly connected to each other by roll-bonding strips of their respective materials and can be directly bonded to each other.

The composite material has two opposing major surfaces (4, 5) formed by the outwardly oriented surfaces of the cover layers (2, 3). The major surfaces (4, 5) can be arranged in planes parallel to one another. The composite material can form a flat cube very approximately, the major surfaces (4, 5) preferably being larger than the sum of all surfaces of the composite material.

The inner core layer (1) and the two outer cover layers (2, 3) are joined to each other via boundary surfaces (6, 7). In the region of the boundary surfaces (6, 7), mixing of the materials of the two outer cover layers (2, 3) and the inner core layer (1) can occur.

For example, a composite material according to the present invention can be produced as follows:

A sandwich consisting of three metal sheets comprising a precipitation-hardening and/or dispersion-hardening copper alloy and/or a precipitation-hardening and/or dispersion-hardening silver alloy as an upper part and a lower part, and a platinum alloy or a palladium alloy (in particular a palladium superlattice) in the middle, are rolled together in a rolling path having a pass reduction of about 60-75%, and the three metal sheets are cold welded to form a composite. In this case, the hardnesses of the materials are very similar, which is achieved when the precipitation-hardening and/or dispersion-hardening copper alloy and/or the precipitation-hardening and/or dispersion-hardening silver alloy in the hardened state is rolled together with a palladium alloy or a platinum alloy in the solution-annealed state (in particular a palladium superlattice alloy according to EP 3 960 890 A1). After rolling to the desired thickness of 30 to 60 μm, the hardness and the electrical conductivity of the platinum alloy or the palladium alloy are adjusted by controlled annealing at 380 ° C for 5 minutes (preferably in vacuum or under protective gas). In this case, the electrical conductivity and the strength of the palladium alloy or the platinum alloy are significantly increased, without the mechanical and electrical properties of the copper alloy and/or the silver alloy being negatively affected (see palladium superlattices according to EP 3 960 890 A1). The palladium alloy can likewise be produced analogously to the method described in EP 3 960 890 A1.

To carry out comparative measurements, a sheet of a palladium alloy having a composition of 36.5 wt. % copper, 10.5 wt. % silver, 1.5 wt. % ruthenium, and the remainder palladium comprising less than 0.1 wt. % impurities, produced according to EP 3 960 890 A1, and two sheets of a precipitation-hardening copper alloy Wieland-K75 (C18070) comprising 0.3 wt. % chromium, 0.1 wt. % titanium, 0.02 wt. % silicon, and the remainder copper, were rolled together. Sequentially, the composite was rolled to a thickness of 54 μm.

Two composite materials according to the present invention produced in this manner are illustrated in FIGS. 3 and 4 as photomicrographs of cross sections of strip-shaped composite materials. The photographs were produced using a Leica DM 6 optical microscope with incident light. For this purpose, the composites were embedded in epoxy resin and ground and polished perpendicular to the rolling plane. The epoxy resin appears black in FIGS. 3 and 4 and is not part of the composite material.

The composite material (A) illustrated in FIG. 3 has an inner core layer (11) made of a palladium alloy having a composition of 36.5 wt. % copper, 10.5 wt. % silver, 1.5 wt. % ruthenium, and the remainder palladium comprising impurities of less than 0.1 wt. %. The core layer (11) is surrounded on both sides by two outer cover layers (12, 13) of a precipitation-hardening copper alloy Wieland-K75 (C18070) comprising 0.3 wt. % chromium, 0.1 wt. % titanium, 0.02 wt. % silicon, and the remainder copper. The two outer cover layers (12, 13) define the composite material (A) at their respective major surfaces (14, 15), which form a major part of the surface of the composite material (A). By means of rolling, the inner core layer (11) and the two outer cover layers (12, 13) are joined to one another and are rigidly connected. There is no intermediate layer. The inner core layer (11) and the two outer cover layers (12, 13) are joined to one another via the boundary surfaces (16, 17). In the region of the boundary surfaces (16, 17), mixing of the materials of the two outer cover layers (12, 13) and of the inner core layer (11) can occur.

The composite material (B) illustrated in FIG. 4 similarly has an inner core layer (21) made of a palladium alloy having a composition of 36.5 wt. % copper, 10.5 wt. % silver, 1.5 wt. % ruthenium, and the remainder palladium including impurities of less than 0.1 wt. %. The core layer (21) is surrounded on both sides by two outer cover layers (22, 23) of a precipitation-hardening copper alloy Wieland-K75 (C18070) comprising 0.3 wt. % chromium, 0.1 wt. % titanium, 0.02 wt. % silicon, and the remainder copper. The two outer cover layers (22, 23) define respective major surfaces (24, 25) of the composite material (B), which form a major portion of the surface of the composite material (B). By means of rolling, the inner core layer (21) and the two outer cover layers (22, 23) are joined to one another and are rigidly connected. Here too, no intermediate layer exists. The inner core layer (21) and the two outer cover layers (22, 23) are joined to one another via the boundary surfaces (26, 27). In the area of the boundary surfaces (26, 27), mixing of the materials of the two outer cover layers (22, 23) and of the inner core layer (21) can occur.

Sequentially, the electrical conductivity was determined by four-point measurement on one of the main surfaces (14, 15, 24, 25) of composite materials (A, B) formed from a precipitation-hardening copper alloy. The four-point measurement method, also called four-point measurement or four-tip measurement, is a method for determining the sheet resistance, i.e. the electrical resistance of a surface or a thin layer. In the method, four measuring tips are moved in a row over the surface of the foil, a known current flows over the two outer measuring tips and the potential difference, i.e. the electrical voltage between the two inner measuring tips, is measured by these two inner measuring tips. Since the method is based on the principle of four-conductor measurement, it is virtually independent of the transition resistance between the measuring tips and the surface (Thomson bridge principle). Adjacent measuring tips have the same distance from each other. The sheet resistance R is derived from the measured voltage U and the current I according to the following formula:

To calculate the resistivity ρ of the layer material from the sheet resistance R , multiply the sheet resistance by the thickness d of the foil (layer thickness).

Electrical conductivity is derived from the reciprocal of resistivity.

Hardness (Vickers hardness test according to DIN EN ISO 6507-1:2018 to -4:2018 with a test force of HV0.05 - 0.4905 N (0.05 kilopond)) and strength were tested by tensile test.

Composite materials (A, B) shown in FIGS. 3 and 4 were produced and investigated.

For comparison, a palladium-copper-silver alloy having the trade name Hera 6321 with the composition of 39 wt.% Pd, 31 wt.% Cu, 29 wt.% Ag, 0.9 wt.% Zn and 0.1 wt. wt.% B was also investigated.

[Table 1]

Measurements of composite materials (A, B) were performed on sheets having a thickness of 54 μm. Hera-6321 alloy was measured on sheets having a thickness of 54 μm.

The sequence of the method according to the present invention is described with reference to FIG. 5 together with FIG. 1 and FIG. 2 below.

In a first working step (101), two strips can be provided or produced: a strip made of a palladium alloy comprising at least 30 wt.% palladium and a strip of a precipitation-hardenable and/or dispersion-hardenable copper alloy comprising at least 90 wt.% copper.

In a second working step (102), strips of palladium alloy can be placed between strips of copper alloy.

In the third working step (103), the strips can be joined together by roll joining, during which the thickness of the strips is reduced.

In an optional fourth working step (104), the thickness of the composite produced in this manner can be reduced by additional rolling in one or more steps to a target thickness (e.g. to 50 μm).

In a fifth working step (105), the composite produced in this manner can be control-annealed (e.g. at 380° C. for 5 minutes) to adjust the desired hardness of the intermediate core layer (1) of the palladium alloy.

In an optional sixth operation step (106), the composite material can be cut or punched into strips.

Sequentially, the final production of the probe needle or bonding strip can optionally take place in a seventh working step (107). For this purpose, for example, the core layers (1) of the strips can be machined as tips of the probe needle.

The features of the invention disclosed in the above description and in the claims, drawings and examples individually and in any desired combination may be essential for implementing the invention in various embodiments.

[Explanation of symbols]

1, 11, 21 inner core layers

1, 11, 21 Outer cover layers

3, 13, 23 Outer cover layers

4, 14, 24 week surface

5, 15, 25 week surface

6, 16, 26 boundary surfaces

7, 17, 27 boundary surface

101 Step 1

102 Second working stage

103 Third stage of work

104 Step 4

105 Step 5

106 Step 6

107 Step 7

Claims (17)

As a composite material for producing a probe needle for electronic testing of semiconductor devices,
The above composite material is strip-shaped and is defined by two mutually parallel major surfaces (4, 5, 14, 15, 24, 25),
The above composite material has a sandwich structure including an inner core layer (1, 11, 21) and two outer cover layers (2, 3, 12, 13, 22, 23) which are laminated perpendicularly to the parallel main surfaces (4, 5, 14, 15, 24, 25),
The inner core layer (1, 11, 21) is arranged between the two outer cover layers (2, 3, 12, 13, 22, 23), and the inner core layer (1, 11, 21) is firmly connected to the two outer cover layers (2, 3, 12, 13, 22, 23) on two opposite sides.
The above two outer cover layers (2, 3, 12, 13, 22, 23) form the above parallel main surfaces (4, 5, 14, 15, 24, 25),
The inner core layer (1, 11, 21) is composed of a palladium alloy containing at least 30 wt.% palladium or a platinum alloy containing at least 30 wt.% platinum,
The above two outer cover layers (2, 3, 12, 13, 22, 23) are
At least one copper alloy of the precipitation-hardening type and the dispersion-hardening type containing at least 90 wt.% copper, or
` At least one silver alloy of the precipitation-hardening type and the dispersion-hardening type containing at least 70 wt.% silver, or
At least one copper alloy of the precipitation-hardening type and the dispersion-hardening type containing at least 90 wt.% copper and at least one silver alloy of the precipitation-hardening type and the dispersion-hardening type containing at least 70 wt.% silver
A composite material composed of: In the first paragraph,
The inner core layer (1, 11, 21) is directly connected to the two outer cover layers (2, 3, 12, 13, 22, 23), or
wherein the composite material comprises the inner core layer (1, 11, 21) and the outer cover layers (2, 3, 12, 13, 22, 23), or
A composite material characterized by being both. In the first paragraph,
A composite material, characterized in that the two outer cover layers (2, 3, 12, 13, 22, 23) are composed of at least one copper alloy of the precipitation-hardening and dispersion-hardening types containing at least 90 wt.% copper. In the first paragraph,
A composite material, characterized in that the inner core layer (1, 11, 21) is composed of a palladium alloy containing at least 30 wt.% palladium. In the first paragraph,
The above composite material,
An electrical conductivity of at least 35% IACS (20.3 10 ⁶ S/m) measured by a four-point measurement method at room temperature on one of the two outer cover layers (2, 3, 12, 13, 22, 23),
At room temperature, a Vickers hardness HV0.05 of at least 170 in the two cover layers (2, 3, 12, 13, 22, 23),
A tensile strength of at least 1000 MPa parallel to the plane of the inner core layer (1, 11, 21) at room temperature, and
A yield strength of at least 950 MPa parallel to the plane of the inner core layer (1, 11, 21) at room temperature.
A composite material characterized by having at least one of: In the first paragraph,
At least one copper alloy of the above precipitation-hardening type and dispersion-hardening type,
At least one copper-chromium alloy of the precipitation-hardening and dispersion-hardening types containing at least 98 wt.% copper, or
A precipitation-hardenable copper-chromium-titanium alloy containing at least 99 wt.% copper, or
A precipitation-hardenable copper-chromium-silver alloy containing at least 98 wt.% copper, or
A copper-silver alloy of at least one of a precipitation-hardening type and a dispersion-hardening type containing at least 90 wt.% copper;
At least one of the above precipitation-hardening and dispersion-hardening types is a silver-copper alloy containing at least 70 wt.% silver;
The above palladium alloy,
A palladium-copper-silver alloy comprising palladium as a main component, wherein the palladium-copper-silver alloy has a weight ratio of palladium to copper of at least 1.05 and at most 1.6, and a weight ratio of palladium to silver of at least 3 and at most 6, wherein the palladium-copper-silver alloy contains more than 1 wt. % and at most 6 wt. % ruthenium, rhodium or ruthenium and rhodium, and at most 1 wt. % other metal elements comprising palladium, copper and silver, and impurities as the remainder, or
A palladium-silver-copper-platinum alloy, or
A palladium-copper-silver-ruthenium alloy, or
A palladium-copper-silver-rhodium alloy, or
A palladium-copper-silver alloy, or
It is a palladium-silver-copper alloy;
The above platinum alloy is a platinum-nickel alloy;
A composite material characterized by at least one of the following: In the first paragraph,
At least one of the above precipitation-hardening and dispersion-hardening copper alloys comprises at least one of a precipitate and a dispersion in an amount of up to 2 wt.%,
A composite material, characterized in that at least one of the above precipitates and dispersed matter comprises at least one element selected from the list consisting of at least 95 wt.% of chromium, titanium, silicon, iron, oxygen, zirconium and silver. In the first paragraph,
A composite material, characterized in that the inner core layer (1, 11, 21) is composed of at least one palladium alloy of the precipitation-hardening type and the dispersion-hardening type, or at least one platinum alloy of the precipitation-hardening type and the dispersion-hardening type. A probe needle comprising a strip of a composite material according to any one of claims 1 to 8. In Article 9,
A probe needle, characterized in that the probe needle has a tip made of the material of the inner core layer (1, 11, 21). A probe needle array in which a plurality of probe needles according to Article 9 are arranged parallel to each other. Use of a composite material according to any one of claims 1 to 8 for testing electrical contact or for making electrical contact or for creating sliding contact. A method for producing a composite material comprising two metal alloys, said method characterized by the following sequential steps:
A) providing a first strip of a palladium alloy comprising at least 30 wt. % palladium or a platinum alloy comprising at least 30 wt. % platinum, and a second strip of at least one of a precipitation-hardening and dispersion-hardening copper alloy comprising at least 90 wt. % copper or at least one of a precipitation-hardening and dispersion-hardening silver alloy comprising at least 70 wt. % silver, and a third strip of at least one of a precipitation-hardening and dispersion-hardening copper alloy comprising at least 90 wt. % copper or at least one of a precipitation-hardening and dispersion-hardening silver alloy comprising at least 70 wt. % silver,
B) a step of arranging the first strip between the second strip and the third strip, and positioning the first strip against the second strip and the third strip, and
C) a step of connecting said first strip to said second strip and said third strip by roll joining said strips positioned opposite each other, said roll joining producing a continuous strip-shaped composite material from the materials of said first strip, said second strip and said third strip. In Article 13,
A method characterized in that after step C), step D) is performed:
D) Temperature treatment of the composite produced in step C) - wherein said material of said first strip undergoes precipitation-hardening or dispersion-hardening or both during said temperature treatment. In Article 13,
By the above method, a composite material according to any one of claims 1 to 8 is produced, or
A method characterized by producing at least one probe needle comprised of a strip of a composite material according to any one of claims 1 to 8 by cutting or punching said composite material. Use of the probe needle of clause 9 for testing electrical contact. Use of the probe needle array of claim 11 for testing electrical contact.

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